U.S. Pat. No. 5,609,114 to Barton, hereinafter referred to as the '114 Patent, discloses a soil opening tool assembly for use with an agricultural implement intended to be moved in a specified line of travel and comprising a first generally upright rotating disc configured to penetrate into the soil to a first depth below the soil surface. The disc is set at a first horizontal angle to the line of travel to provide a leading surface and a trailing surface relative to the direction of travel. The disc is also set at a first angle to the vertical, whereby a top of the disk is inclined generally toward the trailing surface. In one particular embodiment, a disc is toed in 8° horizontally from the line of travel and leans inward 23° to the vertical. According to the '114 Patent, the combined effect of these two angles is that the soil is undercut, lifted and moved by a small amount horizontally, creating an angled furrow into which seed and/or fertilizer is dispensed. The displaced soil exerts a sideways reaction force on the disc, which is transmitted via a rigid connection to the frame of the agricultural implement. An additional disc is also disclosed that engages the soil at a point behind the first disc in the direction of travel to cut a second furrow.
U.S. Pat. No. 6,067,918 to Kirby shows a similar arrangement comprising a first generally upright rotating disc configured to penetrate into the soil to a first depth below the soil surface to create a furrow. A so-called “finger wheel” is also provided to move portions of soil displaced by the disc back over the furrow. To this end, the finger wheel does not penetrate the soil in the manner of the first disc but is, instead, pivotally attached to a frame and is free to move up and down as it rides on the ground.
Although not disclosed in U.S. Pat. No. 5,609,114 to Barton, it can, nevertheless, be advantageous to mount such a soil opening tool assembly to the agricultural implement in a castoring fashion about a pivot located ahead of the assembly in the direction of travel. Such an arrangement is believed to be used, e.g., in the “07 Series Opener” manufactured by the Great Plains Manufacturing Company of Salina, Kans., USA. FIG. 1A is a schematic plan view of such an arrangement for parting soil for placing seed in the ground level G of a field. The pivotal mounting prevents the transmission of the sideways reaction forces to the frame of the agricultural implement. Instead, first and second members 500, 600 run in the ground G at a slight angle W to either side of the direction of travel D, their respective soil-engaging surfaces 501, 601 displacing the soil slightly to cause an opening in the soil so that seed can be introduced and the corresponding sideways reaction forces substantially canceling out. FIG. 1B is a rear elevation of the apparatus of FIG. 1A viewed in the direction of travel (FIG. 1A corresponding to a view taken in the direction of arrow Z in FIG. 1B), from which can be seen that first and second members 500, 600 run at an angle U to either side of the vertical V, perpendicular to the level of the field G. However, the use of two members in this way results in significant disruption of the soil.
With a view to reducing disruption of the soil, U.S. Patent Application Publication No. US 2012/0137942 discloses a soil-opening tool assembly having two discs—a first “parting” or “spreading” disc angled to the direction of travel and to the horizontal as discussed above and a second “coulter” disc that is almost perfectly vertically oriented so as to minimize the fracturing of the soil at the row line.
This disclosure has as an objective the mitigation of problems with such known apparatus.